Prince Philip celebrated his wife's Diamond Jubilee today from the hospital, where we was admitted Monday with a bladder infection.
The prince, who turns 91 this weekend, will remain in the hospital for a few days as a precaution, palace officials say.
Prince Philip was "understandably, disappointed about missing this evening's Diamond Jubilee Concert," the palace said Monday
Prince Charles noted his father's absence as he addressed the crowd. "Only sad thing is that my father couldn't be here with us," Charles said. "If we shout loud enough, he might just hear us in hospital."
His absence was also noticeable today as Queen Elizabeth entered St. Paul's Cathedral on the final day of her celebrating 60 years on the throne.
"When you realized she was on her own and suddenly it reminded us that she's always with Prince Phillip, so very sad for her but he's a tough guy," British journalist and CNN TV-show host Piers Morgan said today on "Good Morning America."
"I mean, it was brutal out there on Sunday. It was a ghastly day so I suppose at the age of 90 it got a bit much for him but the family goes on. They are incredibly stoic people."
Prince Philip spent four nights in the hospital at Christmas after suffering chest pains and underwent a successful coronary stent procedure to clear a blocked artery. Philip, the duke of Edinburgh, married Princess Elizabeth in 1947. She took the throne as queen six years later.
The Diamond Jubilee went on as planned Monday despite the condition of Prince Philip as many members of the royal family, including Charles' wife Camilla, Duchess of Cornwall, and Princes William and Harry sat in a royal box to watch the show.
A quarter of a million people packed into the streets around the palace. Joining Elton John, Stevie Wonder and Paul McCartney outside Buckingham Palace was 1980s favorites Madness, playing from the palace roof. The queen, by the way, arrived a little late, and wearing ear plugs.
The climax was fireworks and the queen pushing a diamond to ignite the so-called national beacon. This was London meets Las Vegas.
The festivities began Saturday at the Epsom Derby for one of the year's biggest horse-racing events. The queen, who is an avid horse breeder and racing fan, has been attending the Epsom Derby since she was a little girl.
Sunday saw more than a million revelers brave Mother Nature as the queen led more than 1,000 vessels -- from kayaks to gondolas -- down a seven-mile stretch of the River Thames in the rain.
Today saw a return to more traditional British pomp and pageantry. The Diamond Jubilee ends today and the queen will deliver a televised address from Buckingham Palace, where she will thank the public for the past four days of celebrations.